Under Murphy's direction, the squad embarks on a mission to snag sexual predators in a more proactive way - by using a fellow officer to entice them in a fake internet stream. This tactic leads to a minor offender named Gordon, but Murphy wants a bigger catch. They lean on Gordon for intel on his worst associates and he clues the team in to a fantasy website focused on young children - and one particularly unsettling participant, Simon Wilkes, who makes his living as a well-respected photographer. Murphy and Rollins go undercover as rich art lovers at one of Wilkes' exhibitions, and Murphy name-drops users from the site, feigning interest in "other" work Wilkes might have for sale. Wilkes takes the bait and, after some discussion outside the gallery, agrees to procure a boy to further their mutual interests.
Armed with the taped conversation, Murphy goes to Barba - who warns that the case lacks a crime and that the government doesn't indict people for imagining things. Everyone on the squad sides with Murphy and he enlists Fin off the books to pose as a human trafficker in an effort to squeeze more dirt on Wilkes. It pays off fast: turns out Wilkes owns a secret soundproof room in his house... filled with instruments of torture. Murphy arrests him and when they case the room, Rollins locates photos that indicate some serious crimes.
Problem is, Wilkes proves he Photoshopped the images and the room comes up clean - not a single stray hair follicle or shred of DNA. Wilkes' lawyer echoes Barba's earlier statement about lack of evidence, so SVU calls up Dr. Huang for a psych evaluation. Although Wilkes sticks with his story about how he's only fantasizing (and not acting) on his impulses, Huang believes Wilkes' torture chamber represents a gun about to go off. They proceed to trial.
Barba tries his best to guide the jury, but without any clear crime, the case appears weak. The team digs deep for any missing leads and lands on something big: Wilkes' ex-wife in Toronto. Turns out she discovered his propensity for dark online material and moved away to protect their son from Wilkes. When they blindside Wilkes in court with his son and ex-wife, he breaks down. He admits that his urges forced a divorce, even though he never acted on them.
But it's not enough to convince the jury. Wilkes walks out a free man and his innocence rattles Amaro the most. It happens to coincide with the frustrating news that Maria and their daughter are moving to Los Angeles - she received an incredible job offer. With all this on his mind, he passes by a playground only to spot Wilkes outside snapping photos of the children at play. Amaro demands he stop, but Wilkes refuses to back down - and Amaro punches him! Wilkes drops to the ground and Amaro continues, pummeling him as a crowd gathers. Police pull him away... and place Amaro in handcuffs.